The long-term objective of this proposal is to develop a small diameter vascular graft that will have improved longevity by creating methods to utilize undifferentiated vascular progenitor cells. The hypothesis of this proposal is that seeding endothelial progenitor cells (EPC) onto small diameter prosthetic grafts prevents thrombosis more efficiently than differentiated endothelial cells, thereby improving the patency rate of the vascular graft. This hypothesis is based on increasing evidence that endothelial progenitor cells may provide a more robust source for reconstitution of the vasculature versus differentiated endothelial cells. The first objective will be to isolate EPCs from porcine bone marrow and confirm phenotypic properties. The second objective will be to evaluate a synthetic graft, polytetrafluoroethylene, seeded with the porcine EPCs. The retention and cell function of the EPC coated synthetic grafts will be determined. The third objective will be to utilize an in vivo model to compare the EPC coated synthetic graft versus a synthetic graft coated with mature endothelial cells verses a non-coated synthetic graft. The endothelial cell retention, function, and patency will be determined. [unreadable] [unreadable]